128 lines
4.5 KiB
C#
128 lines
4.5 KiB
C#
// ==++==
|
|
//
|
|
// Copyright (c) Microsoft Corporation. All rights reserved.
|
|
//
|
|
// ==--==
|
|
/*============================================================
|
|
**
|
|
** Class: WeakReference<T>
|
|
**
|
|
** Purpose: A wrapper for establishing a WeakReference to a generic type.
|
|
**
|
|
===========================================================*/
|
|
namespace System
|
|
{
|
|
using System;
|
|
using System.Runtime.Serialization;
|
|
using System.Security;
|
|
using System.Runtime;
|
|
using System.Runtime.CompilerServices;
|
|
using System.Runtime.Versioning;
|
|
using System.Diagnostics.Contracts;
|
|
|
|
[Serializable]
|
|
// This class is sealed to mitigate security issues caused by Object::MemberwiseClone.
|
|
public sealed class WeakReference<T> : ISerializable where T : class
|
|
{
|
|
// If you fix bugs here, please fix them in WeakReference at the same time.
|
|
|
|
// This field is not a regular GC handle. It can have a special values that are used to prevent ----s between setting the target and finalization.
|
|
internal IntPtr m_handle;
|
|
|
|
// Creates a new WeakReference that keeps track of target.
|
|
// Assumes a Short Weak Reference (ie TrackResurrection is false.)
|
|
//
|
|
public WeakReference(T target)
|
|
: this(target, false)
|
|
{
|
|
}
|
|
|
|
//Creates a new WeakReference that keeps track of target.
|
|
//
|
|
public WeakReference(T target, bool trackResurrection)
|
|
{
|
|
Create(target, trackResurrection);
|
|
}
|
|
|
|
internal WeakReference(SerializationInfo info, StreamingContext context)
|
|
{
|
|
if (info == null) {
|
|
throw new ArgumentNullException("info");
|
|
}
|
|
Contract.EndContractBlock();
|
|
|
|
T target = (T)info.GetValue("TrackedObject", typeof(T));
|
|
bool trackResurrection = info.GetBoolean("TrackResurrection");
|
|
|
|
Create(target, trackResurrection);
|
|
}
|
|
|
|
//
|
|
// We are exposing TryGetTarget instead of a simple getter to avoid a common problem where people write incorrect code like:
|
|
//
|
|
// WeakReference ref = ...;
|
|
// if (ref.Target != null)
|
|
// DoSomething(ref.Target)
|
|
//
|
|
[MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
|
|
public bool TryGetTarget(out T target)
|
|
{
|
|
// Call the worker method that has more performant but less user friendly signature.
|
|
T o = this.Target;
|
|
target = o;
|
|
return o != null;
|
|
}
|
|
|
|
public void SetTarget(T target)
|
|
{
|
|
this.Target = target;
|
|
}
|
|
|
|
// This is property for better debugging experience (VS debugger shows values of properties when you hover over the variables)
|
|
private extern T Target
|
|
{
|
|
[ResourceExposure(ResourceScope.None)]
|
|
[MethodImplAttribute(MethodImplOptions.InternalCall)]
|
|
[SecuritySafeCritical]
|
|
get;
|
|
[ResourceExposure(ResourceScope.None)]
|
|
[MethodImplAttribute(MethodImplOptions.InternalCall)]
|
|
[SecuritySafeCritical]
|
|
set;
|
|
}
|
|
|
|
// Free all system resources associated with this reference.
|
|
//
|
|
// Note: The WeakReference<T> finalizer is not usually run, but
|
|
// treated specially in gc.cpp's ScanForFinalization
|
|
// This is needed for subclasses deriving from WeakReference<T>, however.
|
|
// Additionally, there may be some cases during shutdown when we run this finalizer.
|
|
[ResourceExposure(ResourceScope.None)]
|
|
[MethodImplAttribute(MethodImplOptions.InternalCall)]
|
|
[SecuritySafeCritical]
|
|
extern ~WeakReference();
|
|
|
|
[SecurityCritical]
|
|
public void GetObjectData(SerializationInfo info, StreamingContext context)
|
|
{
|
|
if (info == null) {
|
|
throw new ArgumentNullException("info");
|
|
}
|
|
Contract.EndContractBlock();
|
|
|
|
info.AddValue("TrackedObject", this.Target, typeof(T));
|
|
info.AddValue("TrackResurrection", IsTrackResurrection());
|
|
}
|
|
|
|
[ResourceExposure(ResourceScope.None)]
|
|
[MethodImplAttribute(MethodImplOptions.InternalCall)]
|
|
[SecuritySafeCritical]
|
|
private extern void Create(T target, bool trackResurrection);
|
|
|
|
[ResourceExposure(ResourceScope.None)]
|
|
[MethodImplAttribute(MethodImplOptions.InternalCall)]
|
|
[SecuritySafeCritical]
|
|
private extern bool IsTrackResurrection();
|
|
}
|
|
}
|